The present invention relates to windshield wiper drive trains.
Referring to FIG. 1 a prior art windshield wiper drive train 10 includes a drive shaft 12, a rotating crank arm 14 rigidly attached to drive shaft 12 and a drive bar 16, pivotally joined to crank arm 14. The drive bar 16, in turn, is pivotally joined to and drives a rocker arm 18, which drives a rockshaft 20, to which a windshield wiper may be attached. A problem with this arrangement is caused by the forward (see forward direction arrow 22) offset between drive bar 16 and the point of attachment of rotating arm 14 onto drive shaft 12. This offset is needed for the drive bar 16 to clear the end of the shaft 12, but causes a torque against drive shaft 12 as if to rotate drive shaft 12 in a direction perpendicular to its axis of rotation. This tends to wear out the bearings (not shown) supporting drive shaft 12. Moreover, the pivot joint between rotating arm 14 and drive bar 16, and the pivot joint between drive bar 16 and rockshaft 18 are both wear points that eventually degrade under long term drive train operation.
Furthermore, this type of drive train is not as flexible as is ideally desirable, not being very well adapted to the attachment of additional elements for driving further windshield wipers. Moreover, this type of drive train is not easily adaptable to gearing for different windshield wiper sweep angles.
What is needed then, is a windshield wiper drive train which reduces the wear on the drive shaft bearings by reducing the torque against the drive shaft that is perpendicular to the drive shaft axis of rotation. Also needed is a windshield wiper drive train that is easily gearable to various windshield wiper sweep angles.